Eyeglasses having exchangeable lenses or lens assemblies offer several advantages over conventional eyeglasses having fixed lenses. For example, in the case of sunglasses, different pairs of lenses can be provided for varying light conditions. Some of these lenses are preferably polarized to protect a wearer's eyes against ultraviolet rays. In the case of prescription glasses, lenses manufactured to the current prescription of the wearer can be easily exchanged for the out-of-date prescription lenses. Also, in the case of lens and/or frame damage, a single component can be replaced more economically than purchasing an entirely new pair of eyeglasses.
Exchangeable lens eyeglasses have been known for some time, but older designs have had significant shortcomings in that they are generally of complex mechanical structure, making them expensive to manufacture. Other designs require substantial mutual deformation of the lens and the front component of the frame, making insertion and removal of a lens cumbersome and difficult.
Recently introduced exchangeable eyeglass designs have overcome these shortcomings by making replacement of the lenses more convenient. In one structure disclosed in U.S. Pat. No. 4,176,921, an eyeglass front is made of wire with complete rims (rims completely encompassing the lenses). Welded to the wire rims are two spaced lower prongs for supporting each lens. An additional prong extends adjacent the temple piece, and is either integral with the rim, or is secured thereto in a welded joinder. The lenses, which may be stored without a frame means until ready for use, are inserted from above until they are embraced by the prongs. A metal lever is hinged to a bridge joining the rims and carries a prong for each lens. The lever is rotated downwardly to a holding position, to secure the lenses to the rims. Separate plastic nose pads are attached to the wire front. The eyeglasses shown in this patent have met with widespread success but they require a relatively expensive wire front, which is typically formed of a wire stock, welded in a separate forming step to form a closed loop. Additional welding steps are required to mount lens-engaging hooks to the closed loop. Also, the metal lever must be formed in a separate step and hingedly connected to the wire front.
Frequently, wearers of sunglasses repeatedly store and retrieve their sunglasses several times during a day, during periods of temporary cloudiness, or when entering and exiting buildings, tunnels, or other areas of greatly reduced ambient lighting. Accordingly, collapsible sunglasses have been provided. Examples are disclosed in U.S. Pat. No. 4,549,792 issued Oct. 29, 1985 and in U.S. Pat. No. Des. 276,917 issued Dec. 25, 1984, which include a collapsible wire frame having multiple hinged joints. Lens-mounting portions completely surrounding each lens are hingedly joined together at a hinged bridge portion. Arm-like temple portions are hingedly connected at one end to the wire frames in a conventional manner, and the other end of the temple pieces, which are adapted to engage the ear of a wearer, are also hinged. In both of these patents, the ear-engaging portions of the temple pieces are hinged for downward movement along a horizontal hinge axis. While both glasses have met with general acceptance because of their ability for collapsible storing, exchange of the lenses of these glasses cannot readily be accomplished by a wearer.
Further, designers of eyeglasses in attempting to create a distinctive appearance, have sought to cover substantially the entire frame with the lens portions.